1D- and 2D-NMR spectroscopy studies of the polysaccharide gum from Spondias purpurea var. lutea

Spondias purpurea var. lutea (Anacardiaceae) trees located in Venezuela, South America, produce a clear gum very soluble in water. The polysaccharide, from this gum, contains galactosyl, arabinosyl, xylosyl, rhamnosyl and uronic acid residues. Degraded gums A and B were prepared by mild acid hydrolysis and Smith degradation, respectively. Application of 1D- and 2D-NMR spectroscopy to the original gum and its degraded products, in combination with chemical data, led to confirm that the structure of the original polysaccharide contains 3-O- and 6-O-galactosyl residues, terminal and 3-O-α-l-arabinofuranosyl, terminal rhamnosyl residues and uronic acids, represented by β-d-glucuronic acid and its 4-O-methyl derivative. It was demonstrated that 2D-NMR spectroscopy is a good tool for structural elucidation of complex heteropolysaccharides.